The implantation of medical devices has become a relatively common technique for treating a variety of medical or disease conditions within a patient's body. Depending upon the conditions being treated, today's medical implants can be positioned within specific portions of a patient's body where they can provide beneficial functions for periods of time ranging from days to years. A wide variety of medical devices can be considered implants for purposes of the present invention. Such medical devices can include structural implants such as stents and internal scaffolding for vascular use, replacement parts such as vascular grafts, or in-dwelling devices such as probes, catheters and microparticles for monitoring, measuring and modifying biological activities within a patient's cardiovascular system. Other types of medical implants for treating different types of medical or disease conditions can include in-dwelling access devices or ports, valves, plates, barriers, supports, shunts, discs, and joints, to name a few.
However medical device may migrate from the initial implantation site resulting in loss of efficacy or serious injury. Polished bare metal vascular stents may migrate before endothelialization can occur and exacerbate the initial restriction in coronary blood flow. Moreover, directly coating polished bare metal stents with drugs can result in an immediate release of the drug rather than controlled release. As a result the drug's beneficial effects are diminished, or in some cases localized drug toxicity may occur.
An innovative solution to combat the aforementioned problems with polished bare metal medical devices, particularly vascular stents, has been the development of coating technologies. Polymeric coatings, both bioresorbable and non-bioresorbable are applied directly to the stent surface using spraying, brushing and rolling techniques. The coating can increase the stents biocompatibility and provide a more adhesive stent surface to prevent migration. Furthermore, polymer coating may also have drugs incorporated into the coating to provide the patient with a controlled-release medical device to prevent or treat conditions such as restenosis. Metals and other non-polymers can also be applied to the surface of a medical device. These materials are usually deposited on the device's surface using chemical vapor deposition (CVD) or chemical solution deposition (CSD). However, coatings applied directly to the surface of a polished bare metal device can delaminate; this is especially true for polymers. Delamination can result in unwanted thrombogenic events that may require more aggressive, invasive procedures to correct.
One possible solution that will minimize the aforementioned problems is to provide the implantable medical device with a roughened or textured surface. The elimination of smooth surfaces provides additional surface area for the adhesion of polymers and endothelial cells and provides for superior controlled release of therapeutic agents. Moreover, coatings applied to textured medical devices surfaces are less likely to delaminate.
Textured surfaces enhance controlled drug delivery by providing reservoirs for drugs and thus increase the amount of therapeutic compound that can be loaded onto the device's surface. This in turn increases the time required for physiological fluids to penetrate the device surface and transport the therapeutic compound into the blood stream or adjacent tissue. Recently, titanium provided with textured surfaces has been shown to endothelialize more rapidly and with greater affinity than non-textured titanium surfaces.
Thus, because of the limitations of bare metal medical devices, there remains a need for improved medical devices with textured surfaces.